The present invention relates to a cylinder fuel injection engine controller for controlling the operation of an engine in which fuel is injected directly into the cylinders and, more particularly, to a cylinder fuel injection engine controller capable of enabling an electronic engine control system to achieve an idling speed control operation and a load correcting control operation in satisfactory response.
A prior art cylinder fuel injection engine disclosed in, for example, JP-A No. 7-166916 proposes a technique relating to the control of change between an idling operation in which a rich fuel mixture produced around an ignition plug is ignited and flame propagates for stratified combustion, and a working operation. The prior art technique fully closes an idling bypass valve and a bypass passage if the opening of a throttle valve is greater than an idling opening during the operation of the cylinder fuel injection engine, and controls fuel injection quantity and fuel injection timing according to load on the engine so that stratified combustion occurs when load on the engine is in a low and medium load range and uniform combustion occurs when load on the engine in a high load range.
When the opening of the throttle valve is equal to an opening for idling operation, the idling bypass valve and the bypass passage are fully opened to secure an intake air flow and a volumetric efficiency corresponding to those for full-throttle operation, so that pump loss is reduced and engine speed tends to increase. Therefore, the quantity of fuel injected by an injector is reduced for correction to suppress the increase of engine speed. Thus, the prior art technique increases intake air quantity when it is decided that the mode of operation of the engine changed from a working operation mode to an idling mode to reduce pumping loss and to decrease fuel injection quantity accordingly.
Although the prior art technique concerns the control of intake air quantity and fuel injection quantity when the operating mode of the engine changes between an idling operation mode and a working operation mode, the same concerns nothing about the control of the variation of engine speed due to the variation of the temperature of engine cooling water during idling operation and the control of corrective operations to deal with disturbance such as the application of additional load, such as an air condition system, to the engine. Therefore, the prior art technique is unable to achieve the accurate control of intake air quantity and fuel injection quantity to deal with the variation of engine speed and load on the engine.
Since only stratified combustion is expected for idling operation, nothing is taken into consideration about the control of idling operation using a stoichiometric fuel mixture.
Accordingly, while the engine is cold and stratified combustion cannot be achieved or during stratified combustion after the engine has been warmed up, it is difficult to maintain an idling speed stably if engine speed varies or an additional load is applied to the engine.